Extensible implantable medical lead with sigmoidal conductors

ABSTRACT

An extensible implantable electrical lead includes a lead body having a proximal region and a distal region. The lead body is formed of a polymeric material that is extensible between a first length and a second length. A first plurality of electrical conductors are disposed within the lead body and extend between the proximal region and the distal region. The first plurality of electrical conductors are each electrically insulated and spaced apart from each other and form a side-by-side co-planar first sigmoidal pattern between the proximal region and the distal region.

FIELD

The present disclosure relates to extensible implantable medical leadswith sigmoidal conductors.

BACKGROUND

Implantable medical devices are commonly used today to treat patientssuffering from various ailments. Such implantable devices may beutilized to treat conditions such as pain, incontinence, sleepdisorders, and movement disorders such as Parkinson's disease andepilepsy, for example. Such therapies also appear promising in thetreatment of a variety of psychological, emotional, and otherphysiological conditions.

One known type of implantable medical device, a neurostimulator,delivers mild electrical impulses to neural tissue using an electricallead. For example, to treat pain, electrical impulses may be directed tospecific sites. Such neurostimulation may result in effective painrelief and a reduction in the use of pain medications and/or repeatsurgeries.

Typically, such devices are totally implantable and may be controlled bya physician or a patient through the use of an external programmerCurrent systems generally include a primary cell neurostimulator, a leadextension, and a stimulation lead, and two particular applications ofsystems may be referred to as: (1) spinal cord stimulation; and (2) deepbrain stimulation.

A spinal cord stimulator may be implanted in the abdomen, upper buttock,or pectoral region of a patient and may include at least one extensionrunning from the neurostimulator to the lead or leads which are placedsomewhere along the spinal cord. Each of the leads (to be discussed indetail hereinafter) often includes contains from one to sixteen, or moreelectrodes. Each extension (likewise to be discussed in detailhereinafter) is plugged into or connected to the neurostimulator at aproximal end thereof and is coupled to and interfaces with the lead orleads at a distal end of the extension or extensions.

The implanted neurostimulation system is configured to send mildelectrical pulses to the spinal cord. These electrical pulses aredelivered through the lead or leads to regions near the spinal cord orthe nerve selected for stimulation. Each lead includes a small insulatedwire coupled to an electrode at the distal end thereof through which theelectrical stimulation is delivered. The lead may also include acorresponding number of internal wires to provide separate electricalconnection to each electrode such that each electrode may be selectivelyused to provide stimulation. Connection of the lead to an extension maybe accomplished by means of a connector block including, for example, aseries or combination of set-screws, ball-seals, etc. The leads areinserted into metal set screw blocks, and metal set screws aremanipulated to press the contacts against the blocks to clamp them inplace and provide an electrical connection between the lead wires andthe blocks.

A deep brain stimulation system includes similar components (i.e. aneurostimulator, at least one extension, and at least one stimulationlead) and may be utilized to provide a variety of different types ofelectrical stimulation to reduce the occurrence or effects ofParkinson's disease, epileptic seizures, or other undesirableneurological events. In this case, the neurostimulator may be implantedinto the pectoral region of the patient. The extension or extensions mayextend up through the patient's neck, and the leads/electrodes areimplanted in the brain. The leads may interface with the extension justabove the ear on both sides of the patient. The distal end of the leadmay contain from four to sixteen, or more electrodes and, as was thecase previously, the proximal end of the lead may connect to the distalend of the extension and held in place by set screws. The proximalportion of the extension plugs into the connector block of theneurostimulator.

Both of the spinal cord stimulation and deep brain stimulation implantedsystems traverse portions of the human body that stretch and relax. Toaccount for this stretching and relaxing, the lead and lead extensioncan be looped to allow for stretching and relaxing with the human body.

BRIEF SUMMARY

The present disclosure relates to extensible implantable medical leadswith sigmoidal conductors.

In an exemplary embodiment, an extensible implantable electrical leadincludes a lead body having a proximal region and a distal region. Thelead body is formed of a polymeric material that is extensible between afirst length and a second length. A first plurality of electricalconductors are disposed within the lead body and extend between theproximal region and the distal region. The first plurality of electricalconductors are each electrically insulated and spaced apart from eachother and form a side-by-side co-planar first sigmoidal pattern betweenthe proximal region and the distal region.

In another exemplary, an extensible implantable electrical lead includesa lead body having a proximal region and a distal region. The lead bodyis formed of a polymeric material that is extensible between a firstlength and a second length. A first plurality of electrical conductorsare disposed within the lead body and extend between the proximal regionand the distal region. The first plurality of electrical conductors areeach electrically insulated and spaced apart from each other and form aside-by-side co-planar first sigmoidal pattern from the proximal regionto the distal region. A second plurality of electrical conductors aredisposed within the lead body and extend between the proximal region andthe distal region. The second plurality of electrical conductors areeach electrically insulated and spaced apart from each other and form aside-by-side co-planar second sigmoidal pattern from the proximal regionto the distal region. A layer of the extensible polymeric material isdisposed between the first plurality of electrical conductors and thesecond plurality of electrical conductors.

In another exemplary embodiment, an implantable neurostimulation systemincludes a neurostimulating device and an extensible electrical lead,described herein, electrically coupled to the neurostimulating device.

In another exemplary embodiment, a method includes applying a force of 5N or less to a proximal end and a distal end of an extensible electricallead having a first length. The force increases the first length of theextensible electrical lead by at least 10%. Then the force is removedfrom the extensible electrical lead to return the extensible electricallead to its first length.

BRIEF DESCRIPTION OF THE DRAWING

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a spinal cord stimulation systemimplanted within a human body;

FIG. 2 is a schematic diagram of a deep brain stimulation systemimplanted within a human body;

FIG. 3 is a schematic exploded view of an implantable active medicaldevice;

FIG. 4 is a schematic partial cut-away diagram of an exemplaryextensible lead taken along line 4-4 of FIG. 3;

FIG. 5 is a schematic diagram of the extensible lead in a stretchedstate and a relaxed state; and

FIG. 6 is a schematic cross-sectional diagram of an exemplary extensiblelead taken along line 6-6 of FIG. 3; and

FIG. 7 is a schematic cross-sectional diagram of another illustrativeembodiment of an exemplary extensible lead shown in FIG. 6.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings that form a part hereof, and in which are shown by way ofillustration several specific embodiments. It is to be understood thatother embodiments are contemplated and may be made without departingfrom the scope or spirit of the present disclosure. The followingdetailed description, therefore, is not to be taken in a limiting sense.

All scientific and technical terms used herein have meanings commonlyused in the art unless otherwise specified. The definitions providedherein are to facilitate understanding of certain terms used frequentlyherein and are not meant to limit the scope of the present disclosure.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein.

The term “lead” refers to either or both a lead and a lead extension asdescribed below, unless otherwise noted.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, and 5) and any range within that range.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise. As used inthis specification and the appended claims, the term “or” is generallyemployed in its sense including “and/or” unless the content clearlydictates otherwise.

The term “active implantable medical device” or “implantable signalgenerator” are used interchangeably and includes, for example, a cardiacpacemaker, an implantable defibrillator, a congestive heart failuredevice, a hearing implant, a cochlear implant, a neurostimulator, a drugpump, a ventricular assist device, an insulin pump, a spinal cordstimulator, an implantable sensing system, a deep brain stimulator, anartificial heart, an incontinence device, a vagus nerve stimulator, abone growth stimulator, a gastric pacemaker, and the like.

The present disclosure relates to extensible implantable medical leadswith parallel conductors within the lead forming a sigmoidal pattern(i.e., a repeating s-shaped pattern), where the lead or lead extensionis extensible between a stretched state and a relaxed state. Theseextensible leads are particularly useful as implantable leads forneurostimulator applications where the leads provide spinal cordstimulation and deep brain stimulation and traverse portions of thehuman body that stretch and relax, though the leads are not limited tosuch applications. To account for this stretching and relaxing withinthe patient, the lead is repeatably extensible. The extensible leadsdescribed herein are formed by at least a plurality of electricalconductors that are separated and insulated from each other and form aparallel side-by-side sigmoidal pattern between a proximal region and adistal region of the extensible lead. These sigmoidal pattern electricalconductors are disposed between stretchable or extensible outer layersthat have an extensibility of at least 10% or at least 20% or at least25%, or more. Thus, the extensible lead can be stretched by at least 10%or at least 20% or at least 25%, or more and return to its originallength when relaxed (when a force of 5 N or less is applied). While thepresent disclosure is not so limited, an appreciation of various aspectsof the disclosure will be gained through a discussion of the examplesprovided below.

FIG. 1 is a schematic diagram of a spinal cord stimulation systemimplanted within a human body or patient 28. The implanted spinal cordstimulation system includes an active medical device 20 such as aneurostimulator. The active medical device 20 is coupled to a leadextension 22 having a proximal end coupled to the active medical device20, and a lead 24 having a proximal end coupled to a distal end or leadconnector 32 of the lead extension 22 and a distal end of the lead 24coupled to one or more electrodes 26.

In some embodiments, the lead 24 proximal end is coupled to the activemedical device 20, without a need for the lead extension 22. The spinalcord neurostimulator 20 is illustrated being implanted within the torsoor abdomen of the patient or human body 28. The lead 24 is shown placedsomewhere along the spinal cord 30. In many embodiments, the activemedical device 20 has one or two leads 24 each having four to sixteen,or more, electrodes.

Such a system may also include a physician programmer and a patientprogrammer (not shown). The active medical device 20 can be consideredto be an implantable signal generator of the type available fromMedtronic, Inc., and capable of generating multiple signals occurringeither simultaneously or one signal shifting in time with respect to theother, and having independently varying amplitudes and signal widths.The active medical device 20 contains a power source and the electronicsfor sending precise, electrical signals to the patient to provide thedesired treatment therapy. While the active medical device 20, in manyembodiments, provides electrical stimulation by way of signals, otherforms of stimulation may be used as continuous electrical stimulation.

FIG. 2 is a schematic diagram of a deep brain stimulation systemimplanted within a patient or human body 28. The implanted deep brainstimulation system includes an active medical device 20 such as aneurostimulator. The active medical device 20 is coupled to a leadextension 22 having a proximal end coupled to the active medical device20, and a lead 24 having a proximal end coupled to a distal end or leadconnector 32 of the lead extension 22 and a distal end of the lead 24coupled to one or more electrodes 26.

In some embodiments, the lead 24 proximal end is coupled to the activemedical device 20, without a need for the lead extension 22. The deepbrain neurostimulator 20 is illustrated being implanted within thepectoral region of the patient or human body 28. The lead 24 is shownplaced somewhere on or within the brain. In many embodiments, the activemedical device 20 has one or two leads 24 each having four to sixteen,or more, electrodes.

Such a system may also include a physician programmer and a patientprogrammer (not shown). The active medical device 20 can be consideredto be an implantable signal generator of the type available fromMedtronic, Inc. and capable of generating multiple signals occurringeither simultaneously or one signal shifting in time with respect to theother, and having independently varying amplitudes and signal widths.The active medical device 20 contains a power source and the electronicsfor sending precise, electrical signals to the patient to provide thedesired treatment therapy. While the active medical device 20, in manyembodiments, provides electrical stimulation by way of signals, otherforms of stimulation may be used as continuous electrical stimulation.

FIG. 3 is a schematic exploded view of the implantable stimulationsystem described above that includes an exemplary lead extension 22configured to be physically and electrically coupled between aneurostimulator 20 and lead 24. The implantable stimulation systemdescribed herein allows individual contacts 26 at the distal end of thelead 24 to be addressed individually by the neurostimulator 20 via theindividual insulated electrical conductor extending through the lead 24as described below.

A proximal portion of the lead extension 22 includes a connector 23 orcontacts configured to be received or plugged into connector block 21 ofneurostimulator 20. A distal end of the lead extension 22 includes alead connector 32 including internal contacts configured to receive aproximal end of the lead 24 having contacts 25 thereon.

The lead 24 includes a plurality of insulated electrical conductors eachcoupled at their proximal end to a lead connector 32 via contacts 25 atits proximal end and to contacts of electrodes 26 at its distal end.Some leads are designed to be inserted into a patient percutaneously andsome are designed to be surgically implanted. In some embodiments, thelead 24 may include a paddle (not shown) at its distant end for housingelectrodes 26. In some embodiments, electrodes 26 may include one ormore ring contacts at the distal end of lead 24. Each contact iselectrically coupled to a single insulated electrical conductorextending through the lead 24 as described below.

The lead 24 and/or lead extension 22 has a body formed of an extensiblepolymeric material that allows the lead 24 and/or lead extension 22 tostretch and relax at least 10%, or least 20%, or at least 25%, or atleast 50%, as illustrated in FIG. 5. In some examplary embodiments, theextensible polymeric material (described throughout) is silicone and theinsulated electrical conductor are configured to allow the lead 24and/or lead extension 22 to stretch and relax at least 10%, or least20%, or at least 25%, or at least 50%, as illustrated in FIG. 5. Theextensibility values reported herein are based on an applied force of 5N or less.

FIG. 4 is a schematic partial cut-away diagram of an illustrativeextensible lead taken along line 4-4 of FIG. 3. FIG. 5 is a schematicdiagram of the extensible lead in a stretched state and a relaxed state.The extensible lead includes a lead body 40 extending between a proximalregion 42 and a distal region 41. FIG. 6 is a schematic cross-sectionaldiagram of the extensible lead taken along line 6-6 of FIG. 3. FIG. 4shows layers 41, 50, 42, 60 of the lead body 40 progressively removedfrom the lead body 40 for illustration proposes. FIG. 7 is a schematiccross-sectional diagram of another illustrative embodiment of theextensible lead shown in FIG. 6. FIG. 7 illustrates a lead body 40having a single plurality of electrical conductors 50 disposed withinthe lead body 40 and extending between the proximal region 42 and thedistal region 41, where the electrical conductors 50 are eachelectrically insulated and spaced apart from each other and form aside-by-side co-planar first sigmoidal pattern.

The lead body 40 is formed of a polymeric material that is extensiblebetween a first length L and a second length L+ΔL, where the secondlength is greater than the first length by at least 10%, or least 20%,or at least 25%, or at least 50%. This increase in length isaccomplished by application of a force of 5 N or less. Upon removal ofthe force, the lead body 40 relaxes, contracts, or returns to itsoriginal length L. The lead body can be cycled between the first lengthand the second length thousands of times or more.

In some exemplary embodiments, the lead body 40 can include an innerlayer 42 of extensible polymeric material disposed between a firstplurality of parallel electrical conductors 50 forming a first sigmoidalpattern and a second plurality of parallel electrical conductors 60forming a second sigmoidal pattern (see FIG. 6). In many of theseembodiments, the lead body 40 includes outer layers 41, 43 of extensiblepolymeric material disposed on opposing outer surfaces of the first andsecond electrical conductors 50, 60. FIG. 6 illustrates theconfiguration of the outer layers 41, 43 the first and second electricalconductors 50, 60 and the inner layer 42 all in co-planar relation toeach other. FIG. 7 illustrates the configuration of extensible outerlayers 41, 43 disposed on opposing sides of the first plurality ofparallel electrical conductors 50.

In some exemplary embodiments, the outer layers 41, 43, first and second(when present) electrical conductors 50, 60 and the inner layer (whenpresent) 42 are fixed at the proximal region 42 and a distal region 41of the lead body 40. In some exemplary embodiments, the first and second(when present) electrical conductors 50, 60 are fixed to the inner layer(when present) 42 and/or the outer layers 41, 43 at discrete locationsor continuously along the length of the lead body 40. In someembodiments the inner layer (when present) 42 or the outer layers 41, 43are loosely disposed adjacent to the first and second (when present)electrical conductors 50, 60 between the proximal region 42 and a distalregion 41 of the lead body 40.

The first and second (when present) electrical conductors 50, 60 areformed of a plurality of parallel insulated electrical conductors thatare spaced apart from one another any useful distance S (see FIG. 6 andFIG. 7). In many embodiments the first and second (when present)electrical conductors 50, 60 have adjacent (and coplanar) electricalconductors spaced apart from one another a distance in a range from 0.5to 5 diameters, or from 0.5 to 3 diameters, or from 0.5 to 2 diameters,or at least half of a diameter, or at least 1 diameter or at least twodiameters. Having the parallel adjacent insulated electrical conductorsspaced apart from each other can assist in allowing the lead body tocontract or narrow as the lead body is stretched.

In many examplary embodiments, the extensibility of the extensiblepolymeric layers 41, 42, 43 substantially match the stretchability ofthe first and second (when present) electrical conductors 50, 60 fromthe sigmoidal configuration to a more elongated sigmoidal configurationand even to a planar parallel configuration (representing a maximumstretched length L+ΔL). The extensible polymeric layers 41, 42, 43 areformed of an extensible polymeric material that allows the lead body 40to stretch and relax at least 10%, or least 20%, or at least 25%, or atleast 50%, as illustrated in FIG. 5. In many embodiments, the extensiblepolymeric material is silicone and the insulated electrical conductors50, 60 are configured to allow the lead body 40 to stretch and relax atleast 10%, or least 20%, or at least 25%, or at least 50%, asillustrated in FIG. 5. The extensible polymeric layers 41, 42, 43 canassist in returning the parallel insulated electrical conductors 50, 60to their relaxed (sigmoidal) state after the lead body 40 has beenstretched.

The first plurality of parallel electrical conductors 50 forming thefirst sigmoidal pattern are disposed within the lead body 40 and extendbetween the proximal region and the distal region of the lead body 40.The first plurality of parallel electrical conductors 50 are eachelectrically insulated from each other separated from one another fromthe proximal region to the distal region. The second plurality ofparallel electrical conductors 60 forming the second sigmoidal patternare disposed within the lead body 40 and extend between the proximalregion and the distal region of the lead body 40. The second pluralityof parallel electrical conductors 60 are each electrically insulatedfrom each other separated from one another from the proximal region tothe distal region.

In many embodiments, the lead body 40 forms a flat or planar lead bodyconfiguration where the cross-sectional shape approximates a rectangleprofile (as illustrated in FIG. 6 and FIG. 7). In these embodiments therectangle profile has an aspect ratio (thickness to width) in a rangefrom 1:1 to 1:20, or from 1:2 to 1:10, or from 1:4 to 1:10. In manyembodiments, the first plurality of parallel electrical conductors 50forming the first sigmoidal pattern is not in registration (i.e., is outof phase) with the second sigmoidal pattern formed by the secondplurality of parallel electrical conductors 60. It may be preferred tohave the first sigmoidal pattern oppose the second sigmoidal pattern. Inother words the two sigmoidal patterns can be described as being out ofphase by 180 degrees. In many embodiments the first plurality ofparallel electrical conductors 50 forms a first sigmoidal pattern thathas the same period with the second sigmoidal pattern formed by thesecond plurality of parallel electrical conductors 60. In some of theseembodiments the first sigmoidal pattern is out of phase by 180 degreeswith the second sigmoidal pattern.

While the exemplary illustrated embodiment includes four parallelinsulated electrical conductors for the first plurality of parallelelectrical conductors 50 and four parallel insulated electricalconductors for the second plurality of parallel electrical conductors 60each plurality can include any useful number of insulated electricalconductors such as, for example, from 3 to 16, or from 4 to 12, or from4 to 8, as desired. The first plurality of parallel electricalconductors 50 can be arranged in a single plane (e.g., X-Y plane) andthe second plurality of parallel electrical conductors 60 can bearranged in a single plane (e.g., X-Y plane) that is parallel to theplane that contains the first plurality of parallel electricalconductors 50.

The conductors described above that form the first and second sigmoidalpatterns can have any useful diameter. In many embodiments, the barewire electrical conductors 61, 51 have a diameter in a range from 50 to250 micrometers, or from 100 to 150 micrometers and the insulator layer52, 62 can add from 15 to 50 micrometers to the electrical conductordiameter. Thus, in many embodiments, the insulated electrical conductors50, 60 have a diameter in a range from 65 to 300 micrometers, or from115 to 200 micrometers. The insulator layer can be formed of any usefulelectrically insulating material such as, for example, a polymericmaterial. In some embodiments, the electrically insulating materialincludes silicone. In many embodiments, the electrical conductors and/orthe insulated electrical conductors 50, 60 used to form the first andsecond sigmoidal patterns have the same or substantially the samediameter. In many embodiments, the insulated electrical conductors 50,60 have a circular cross-sectional profile, however in some embodimentsthe insulated electrical conductors 50, 60 have a rectangularcross-sectional profile.

The lead body 40 extends between a proximal region 42 and a distalregion 41. As shown in FIG. 3 and FIG. 5, stimulating electrodes 26 arelocated at the distal region 41 and contacts 25 are located at theproximal region 42. Each insulated electrical conductor 50, 60 used toform the first and second sigmoidal patterns can be individuallyaddressed between a single contact 25 and a single electrode 26 suchthat a particular electrode 26 can be individually activated via thecontact and a single insulated electrical conductor.

Thus, exemplary embodiments of the EXTENSIBLE IMPLANTABLE MEDICAL LEADWITH SIGMOIDAL CONDUCTORS are disclosed. One skilled in the art willappreciate that the present disclosure can be practiced with otherembodiments. The disclosed embodiments are presented for purposes ofillustration and not limitation, and the present disclosure is limitedonly by the claims that follow.

1. An extensible implantable electrical lead comprising: a lead bodyhaving a proximal region and a distal region, the lead body formed of anextensible polymeric material that is extensible between a first lengthand a second length, the second length being greater than the firstlength; and a first plurality of electrical conductors disposed withinthe lead body and extending between the proximal region and the distalregion, the first plurality of electrical conductors are eachelectrically insulated and spaced apart from each other and form aside-by-side co-planar first sigmoidal pattern between the proximalregion and the distal region; and further comprising a second pluralityof electrical conductors disposed within the lead body and extendingbetween the proximal region and the distal region, the second pluralityof electrical conductors are each electrically insulated and spacedapart from each other and form a side-by-side co-planar second sigmoidalpattern from the proximal region to the distal region, and a layer ofthe extensible polymeric material is disposed between the firstplurality of electrical conductors and the second plurality ofelectrical conductors.
 2. An extensible implantable electrical leadaccording to claim 1, wherein the first plurality of electricalconductors have substantially the same outer diameter.
 3. An extensibleimplantable electrical lead according to claim 1, wherein the secondlength is at least 10% greater than the first length.
 4. An extensibleimplantable electrical lead according to claim 1, wherein the secondlength is at least 20% greater than the first length.
 5. An extensibleimplantable electrical lead according to claim 1, wherein the extensiblepolymeric material comprises silicone.
 6. An extensible implantableelectrical lead according to claim 1, wherein the lead body furthercomprises a plurality of contacts or electrodes at the distal region ofthe lead body and a plurality of contacts at the proximal region andeach electrical conductor electrically connects a single distal regioncontact or electrode with a proximal region contact.
 7. An extensibleimplantable electrical lead according to claim 1, wherein eachelectrical conductor is spaced apart from an adjacent co-planarelectrical conductor by at least a distance equal to half of a diameterof each electrical conductor.
 8. An extensible implantable electricallead according to claim 1, wherein the lead body forms a planar leadbody having a rectangular cross-section profile.
 9. (canceled)
 10. Anextensible implantable electrical lead according to claim 1, wherein thelead body comprises an outer layer of the extensible polymeric materialdisposed on opposing outer surfaces of the first plurality of electricalconductors and second plurality of electrical conductors, forming aplanar lead body having a rectangular cross-section profile.
 11. Anextensible implantable electrical lead according to claim 1, wherein thefirst plurality of electrical conductors equals the second plurality ofelectrical conductors.
 12. An extensible implantable electrical leadaccording to claim 1, wherein the first sigmoidal pattern is out ofphase with the second sigmoidal pattern.
 13. An extensible implantableelectrical lead according to claim 1, wherein the first sigmoidalpattern is out of phase by 180 degrees with the second sigmoidalpattern.
 14. An extensible implantable electrical lead according toclaim 1, wherein each of the second plurality of electrical conductorare spaced apart from each other by at least a distance equal to adiameter of adjacent second plurality of electrical conductors.
 15. Animplantable neurostimulation system comprising a neurostimulatingdevice; and an extensible electrical lead electrically coupled to theneurostimulating device the extensible lead comprising: a lead bodyhaving a proximal region and a distal region, the lead body formed of anextensible polymeric material that is extensible between a first lengthand a second length, the second length being greater than the firstlength; and a first plurality of electrical conductors disposed withinthe lead body and extending between the proximal region and the distalregion, the first plurality of electrical conductors are eachelectrically insulated and spaced apart from each other and form aside-by-side co-planar first sigmoidal pattern between the proximalregion and the distal region; and further comprising a second pluralityof electrical conductors disposed within the lead body and extendingbetween the proximal region and the distal region, the second pluralityof electrical conductors are each electrically insulated and spacedapart from each other and form a side-by-side co-planar second sigmoidalpattern from the proximal region to the distal region, and a layer ofthe extensible polymeric material is disposed between the firstplurality of electrical conductors and the second plurality ofelectrical conductors.
 16. An implantable neurostimulation systemaccording to claim 15, wherein the extensible electrical lead is a leadextension that electrically couples the neurostimulating device to aproximal region of a lead having a plurality of contacts at a distalregion of the lead.
 17. A method comprising: applying a force of 5 N orless to a proximal end and a distal end of an extensible electrical leadhaving a first length, the force increasing the first length of theextensible electrical lead by at least 10% the extensible leadcomprising: a lead body having a proximal region and a distal region,the lead body formed of an extensible polymeric material that isextensible between a first length and a second length, the second lengthbeing greater than the first length; and a first plurality of electricalconductors disposed within the lead body and extending between theproximal region and the distal region, the first plurality of electricalconductors are each electrically insulated and spaced apart from eachother and form a side-by-side co-planar first sigmoidal pattern betweenthe proximal region and the distal region; and further comprising asecond plurality of electrical conductors disposed within the lead bodyand extending between the proximal region and the distal region, thesecond plurality of electrical conductors are each electricallyinsulated and spaced apart from each other and form a side-by-sideco-planar second sigmoidal pattern from the proximal region to thedistal region, and a layer of the extensible polymeric material isdisposed between the first plurality of electrical conductors and thesecond plurality of electrical conductors; and removing the force fromthe extensible electrical lead to return the extensible electrical leadto its first length.
 18. A method according to claim 17, wherein theapplying step increases the first length by at least 20%.
 19. A methodaccording to claim 17, wherein the applying step increases the firstlength by at least 25%.
 20. A method according to claim 17, furthercomprising implanting the extensible electrical lead in a patient.